Combination of digital images and laser light to predict moisture content and color of bell pepper simultaneously during drying

Publication Type

Journal contribution (peer reviewed)

Authors

Romano, G; Argyropoulos, D; Nagle, M; Khan, MT; Müller, J

Year of publication

2012

Published in

Journal of Food Engineering

Band/Volume

109/

Page (from - to)

438-448

Keywords

moisture

Optical devices are being increasingly used for more accurate and faster ways to investigate quality
parameters of agricultural products. The main task of this research is to evaluate the use of a CCD camera
in combination with laser diodes emitting at 532 nm and 635 nm to monitor changes in moisture content
of red, yellow and green bell pepper during drying. Moreover, the feasibility of using the CCD camera
alone to analyze color changes during drying, in alternative to the colorimeter, is assessed. Results
showed that scattering area and light intensity were able to predict moisture content changes of bell pepper
during drying. While excellent correlations were obtained for yellow colored samples (R = 0.93 and
RMSEP = 7.28), the behavior of green and red wavelengths in peppers with red and green color, respectively,
may raise some doubt on the ability to predict moisture content (R = 0.33 and RMSEP > 22). Additionally,
light scattering varied according to the different depths on the surface where the images were
taken. Furthermore, it was concluded that a change in tissue structure during drying may have caused
dispersion of photons through the surface resulting in varying degrees of scattering. The presented technique
based on a digital camera and laser diodes shows the potential to be applied in the future as a fast
and modern method for in-line measurements of monitoring moisture content during drying. Digital
images in terms of RGB values have been demonstrated to be a promising alternative to monitor changes
of L⁄ (R = 0.87 and R = 0.90), and a⁄ values (R = 0.93 and R = 0.97), during drying of yellow and green pepper.
Extensive studies are still required to determine the suitability of digital images for analysis of b⁄ values
at different colors of bell pepper.